1. Field of the Invention
The invention relates to the field of telecommunications, and in particular, to wireless mobile telecommunications transmission/reception control based on relative geographical position information.
2. Background Information
Mobile communication, e.g., cellular telephone communication, usually involves the exchange of radio transmission signals between a mobile unit (mobile client) and a base station. With ground-based mobile units, these radio transmission signals are often subject to a number of phenomena which can limit communication, including naturally occurring variations in geography, such as hills and valleys. This is because mobile communications is often based on a point-to-point, line-of-sight transmission path between the mobile unit and the base station. Terrain variations, man-made obstacles, and the like, can interfere with the communications, resulting in what are called xe2x80x9cdead zones.xe2x80x9d
Dead zones are geographical areas where communications signals do not penetrate or are too weak to provide for reliable communications. Such zones can be caused by radio signal shadowing, e.g., as occur when a mobile unit travels behind a hill, under a bridge or through a tunnel, or they can be due to signal reflections/images in radio signal patterns caused by the signals bouncing off radio-reflective objects, such as buildings, etc. An absorption of signals can also occur under certain circumstances resulting in a dead zone. For example, some non-reflective (xc2xc wavelength) coatings are known which are generally absorptive of particular radio signals, and such a phenomena can occur naturally as well.
Even though the cause of the dead zones may not change position, the physical extent of these dead zones can change over the course of a day due to atmospheric condition changes, for example, and they may even have a different physical extent from one season to the next. To provide reliable and efficient communications with mobile units in communication areas where dead zones are present, attempts are sometimes made to minimize their effects. For example, additional antennae may be placed to cover the areas affected. However, because of cost and other considerations, it is virtually impossible to eliminate all dead zones.
With the advent of enhanced mobile personal communications equipment beyond the simple voice cell-phone to relatively more complex mobile data transmission and receiving devices, dead zones have become more than just a simple annoying interruption of a telephone conversation.
Some examples of the types of communications that are being considered, developed and/or implemented include traffic information updates, static and dynamic point-to-point routing, remote diagnostics, user comfort settings, and regional radio station detection and selection. A Concept Car was shown at the 1997 COMDEX show in Las Vegas, which incorporates so-called xe2x80x9ctelematics.xe2x80x9d Telematics can include in car communication with the Internet for accessing e-mail, web pages, personal preference items (stocks, weather, sports, etc), memos, navigation, car security/safety (911), as well as being expanded for video/movies for the passengers, for example. Along with these personal communications tools, if appropriate, an interface to the on-board vehicle control and diagnostic computer bus through an engine compartment firewall could be provided so that the user or remote fleet management system (for trucks) can run diagnostics on the automobile engine, as well as monitor vehicle progress on a route.
It should be apparent that, should a mobile unit enter a dead zone during a data transmission, substantial time and bandwidth may be wasted attempting a complete retransmission of the data when communication is impossible. More serious consequences could result due to a partially garbled and/or delayed transmission. For example, an investor might be attempting to conduct an on-line trade in the stock market where a delay of even a few minutes could mean the difference between a profitable trade and a missed opportunity.
It can further be appreciated by those skilled in the art that mobile communications networks generally have to handle a large number of simultaneous mobile units attempting to communicate with a base station at any given time. To accommodate the units, multiplexing techniques are used where, for example, the limited base station bandwidth is divided into time slots and the units are time-division multiplexed. Generally, there is no prioritizing of transmission slot sharing and the resources are divided equally among units requesting transmission.
The present inventors realized that it would be advantageous to know exactly where the dead zones are relative to the mobile units in a communication system so that such problems could be anticipated and appropriate measures taken.
According to a copending application assigned to the same assignee as the present application, which became known to the present inventors subsequent to making their invention, Ser. No. 09/133,649, filed Aug. 13, 1998, entitled xe2x80x9cERROR CORRECTION FOR WIRELESS NETWORKSxe2x80x9d (attorney docket YO998167): xe2x80x9cmethods, devices and systems are presented for providing service providers and/or end users of mobile stations to monitor and/or report regions with high error rates and/or dead zones . . . each mobile station periodically compares its current location with the data base [of locations with errors] . . . [T]he results of this comparison enables the mobile unit to anticipate connection problemsxe2x80x9d (Abstract, see also page 20, line 16 to page 21, line 18). The mobile unit uses an on-board GPS (global positioning satellite system) to get its current location (see page 8, lines 4 to 20).
Further, according to the copending application, the mobile units include an error rate monitor to monitor a reception error rate, and a message processor to send an error message to a base station when the error rate rises above a preset threshold (page 21, line 19 to page 22, line 8). A database that contains records of all error messages may be maintained, used to map areas of reception dead zones, and queried by a mobile user to determine if the user is entering a dead zonexe2x80x94the base station may then inform the mobile user of an appropriate step to take to maintain connectivity (page 22, line 15 to page 23, line 2). According to the copending application, a user may be given a route to avoid dead zones, and/or given a warning signal that the user is approaching a dead zone (page 23, lines 12 to 17).
However, sometimes taking steps to maintain connectivity may not be convenient or even possible. For example, if the mobile unit is a large truck or even a passenger car, it may be that there is no place to pull over the mobile unit, turn around or otherwise take another route to avoid a dead zone. In some areas, such as the U.S. East Coast Interstate 95 North-South corridor, alternative routes are either limited or non-existent.
In view of the above discussion, it is apparent that a need exists for additional ways to overcome the problems of potential data transmission losses and delays caused by unexpected or expected entries into dead zones.
A network processing system which ensures processing continuity by holding data received from a network accessible application for transmission to a mobile unit only when the mobile unit is in actual wireless communication with the network is known (see, e.g., U.S. Pat. No. 5,564,070).
A hierarchical communication system which provides adaptive data rate selection based on the detected quality of communication, and which provides for resolving conflicts among competing communications protocols on a priority basis, is known (see, e.g., U.S. Pat. No. 5,696,903).
A way of locating mobile end users of a communications system and routing messages to the end users as they roam between communication networks having local servicing offices is known. This is based on user specific information which is stored by the local servicing offices, and can be used to track the end users. Stored messages and data can then be routed and forwarded to the end users (see, e.g., U.S. Pat. No. 5,659,596).
A method of controlling communication services based on geographical information is known. Communication is restricted if the unit requesting communications services is within a restricted geographical location, such as in proximity to a hospital having sensitive RF (radio frequency) medical devices, or granted if the unit is not within a restricted location (see U.S. Pat. No. 5,778,304).
A global positioning system (GPS) is known in which a mobile or stationary unit can ascertain its present location, latitude, longitude and altitude, by the detection and processing of signals from geo-synchronous satellites. Such systems are used to navigate aircraft as well as ground based vehicles (see, e.g., U.S. Pat. No. 5,606,506) and have been used to track mobile stations (see, e.g., U.S. Pat. No. 5,564,079). A GPS system has been integrated with an inertial navigation system (see, e.g., U.S. Pat. No. 5,606,506).
The GPS has been used in conjunction with telephony to combine location identification with telephone number identification so that the geographical location of a particular telephone number user can be ascertained (see, e.g., U.S. Pat. No. 5,727,057).
The GPS has also been used in communication configuring of digital equipment based on its location using configuration data stored in the digital equipment (see, e.g., U.S. Pat. Nos. 5,635,940 and 5,581,261).
Another mobile communications tracking system which does not rely on GPS but instead uses signals exchanged with nearby cells is also known (see, e.g., U.S. Pat. No. 5,767,788).
However, despite these previous systems, there still existed a need for an improved mobile communication system. In prior systems, the transmitter of information may be notified by the receiver that some transmitted information was not received. The data may then be retransmitted or a time delay before retransmission may be used. In either case, if the reason for the lack of reception is due to the relative location of transmitter and receiver, i.e., relative to a dead zone, this information is not known by the transmitter or receiver. Wasted time and bandwidth may occur, if for example, a transmitter tries to repeat a transmission when the receiver is totally incapable of receiving the information. This might occur, for example, it the receiver is in a vehicle and the vehicle is inside of a tunnel which is naturally shielded from radio transmissions.
It is, therefore, a principle object of this invention to provide a method and apparatus for mobile client-based station communication based on position information.
It is another object of the invention to provide a method and apparatus that solves the above mentioned problems so that mobile communications can be accomplished more effectively.
These and other objects of the present invention are accomplished by the method and apparatus disclosed herein.
Considering the state of the art, the inventors recognized that data loss could be avoided if a communications system gave priority to a mobile unit transmitting or receiving data which was approaching a dead zone. Further, if the mobile unit knew of the approach of a dead zone, data transmission, either to or from the mobile unit in question, could be expedited or delayed. If the system could predict when a mobile unit would exit a dead zone, more efficient use of communications resources could be accomplished. Data to be transmitted to the mobile unit from the base station could be stored in anticipation of dead zone exit. Likewise, the mobile unit could buffer data transmission to the base station while in the dead zone in the same way.
Therefore, according to an aspect of the invention, scheduling of transmissions over any wireless system based on knowledge of the position of a mobile client (mobile unit) by another system is provided.
According to another aspect of the invention, the mobile client position information can be used together with stored position information about one or more dead zones to prioritize the transmission of data between a base station and the mobile client. For example, the position information allows the scheduling of data exchanges so that data transmissions are sure to be completed before a dead zone is entered. The type of data to be transmitted can be considered in the prioritization.
According to an aspect of the invention, from the geographical position information, data transfer between a mobile client and base station may be withheld until a more favorable geographic location becomes available. The data to be transmitted can be stored and transmission delayed until after a dead zone is exited, for example.
According to another aspect of the invention, from successive position readings, a trajectory of the mobile client can be determined. Based on the trajectory of the mobile client, a prediction of when more favorable transmission conditions will exist can be determined and used to prioritize communications in an efficient manner.
According to another aspect of the invention, the location of a mobile client relative to a base station can be provided by a positioning system, such as a Global Positioning Satellite/System (GPS), Doppler radar, visual contact, triangulation, an inertial guidance system (IGS), or any other equivalent geo-positioning system.
According to another aspect of the invention, in the base station, the respective locations of a plurality of dead zones are stored. For a ground-based mobile unit, the location of a dead zone can be stored, for example, as a two dimensional simplification using a sequence of (xij, yij) coordinates where i=1, . . . N and N is chosen to be a suitably large integer so that each jth dead zone is represented faithfully. For the purposes of estimating the available transmission time before the mobile client enters a dead zone, the boundaries of the dead zone are progressively refined as the mobile client approaches using a fractal-type methodology, minimizing the computations required to be performed by a processor at the base station, mobile client, or both.
According to another aspect of the invention, mobile client position information is communicated to the base station and information about the estimated time until the mobile client enters a dead zone is provided by the base station to the mobile client, implementing a two-way protocol.
According to another aspect of the invention, when the mobile client is in the dead zone, it uses information about the extent of the dead zone provided the base station to estimate the time when communication with the base station will again be possible.
According to another aspect of the invention, information about the boundaries of a dead zone, which may be dynamic, are included in the transmissions between the mobile unit and the base station after the mobile client has exited the dead zone. The base station uses this information to dynamically update a database containing the location and extent of dead zones.
According to another aspect of the invention, an iterative refinement of an estimate of an exact interception point with the dead zone continues up until the mobile client actually enters the dead zone. This refinement process a fractal-type process and the scale of the dead zone boundary is constantly improved, i.e., with increasing magnification, as the mobile client approaches the dead zone.
According to another aspect of the invention, even though when the mobile client is in the dead zone there is no further communication possible with the base station (by definition), the mobile client is still aware of its position through other means, that is, from geo-positioning data from a satellite system, e.g., GPS, or from some other system, e.g., an internal inertial guidance system. Before entering the dead zone, the base station may have sent relevant dead zone coordinates for the boundary at which point the mobile client is expected to exit the dead zone based on current trajectory, and Calculations can then be performed by a processor in the mobile client to anticipate dead zone exit. Alternatively, before the mobile client entered the dead zone, information concerning the expected time when the dead zone will be exited can be sent from the base station and the mobile client can anticipate dead zone exit based on time measurements. When there is a difference between the expected and actual dead zone exit time/coordinates, these differences can be used to adjust stored dead zone boundaries.
According to another aspect of the invention, under some circumstances, the mobile client will become immobile for an extended period of time. For example, a mobile client may encounter an unexpected delay. When the base station and/or mobile client does not establish communication within some tolerance surrounding the expected time of emergence from a dead zone, the communication is placed in a hold queue. When communication is again possible, the mobile client provides its position information to the base station and the communication link is removed from the hold queue.
According to another aspect of the invention, the exchange of position information is facilitated by use of a data transmission protocol that accommodates position information, for example, GPS data or other system position information. Assuming packet transmission (which is optimal in general for mobile communication), some packets include the position information (e.g., GPS data). Additionally, some packets can include the estimated time before a mobile client will enter a dead zone and/or how long communication will be interrupted. This information can be used to schedule transmissions between base station and mobile client.
According to another aspect of the invention, the above mentioned problems are solved by considering stored geographical information when a client/server communication is negotiated.
According to another aspect of the invention, known dead zone location information is used to schedule communication with a mobile unit, and dynamic updating of the stored dead zone location information based on detection of changed dead zone boundaries is also enabled.
The above-mentioned aspects of the invention, and other advantages and benefits of the invention which flow naturally therefrom, solve a number of problems and overcome a number of limitations related to data communication over a wireless mobile communication system, such as radio or optical, which is naturally interrupted by many obstacles in a transmission path.
According to an aspect of the invention, via a GPS, or other positioning system, for example, Doppler radar, inertial guidance, or another position device, located at a transmitter (server) and/or receiver (client), the transmission of data is biased towards those receivers which are currently in a clear reception path, i.e., not in a dead zone. This location knowledge permits a transmitter to decide when and to which mobile client information is sent, and thereby avoid wasted transmission resources.
According to another aspect of the invention, data loss is avoided because the communications system can grant priority to a unit transmitting/receiving data as it approaches a dead zone. In prior systems, generally there is no prioritizing of transmission slot sharing and the resources are divided equally among units requesting transmission in multiplexed mobile communications.
According to another aspect of the invention, data transmission can be delayed and the data stored in a hold queue when a mobile unit is approaching or is inside a dead zone, to be later transmitted after the mobile unit leaves the dead zone.
According to another aspect of the invention, successive mobile unit positions can be used to determine a rate and direction of travel of the mobile unit, and the rate and direction of travel (trajectory) can be used to predict when the mobile unit will enter and leave a particular dead zone so that communication can be coordinated therewith.
These and other aspects of the invention will become apparent from the detailed description set forth below.